New insights into Eragrostis curvula's sexual and apomictic reproductive development

Maria Cielo Pasten ^1,2 Jose Carballo ¹ Alejandra Raquel Díaz ^1,3 Chiara Mizzotti ⁴ Mara Cucinotta ⁴ Lucia Colombo ⁴ Viviana Carmen Echenique ^1,2* Marta Adelina Mendes ^4*

• ¹ CONICET Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS), Bahía Blanca, Argentina
• ² Department of Agronomy, National University of the South, Bahía Blanca, Buenos Aires, Argentina
• ³ Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, Bahía Blanca, Argentina
• ⁴ University of Milan, Milan, Lombardy, Italy

Apomixis, defined as asexual propagation by seeds, is considered of great importance for agriculture as it allows the fixation of desired traits and its propagation through generations. Eragrostis curvula (Schrad.) Ness, is a perennial grass that comprises a polymorphic complex including sexual and diplosporous apomictic cytotypes, where all apomicts are polyploids. In this study we present the first detailed description of female and male gametophyte development in E. curvula through confocal laser microscopy, contrasting three genotypes: the fully apomictic Tanganyika, the facultative apomictic Don Walter (DW), and the sexual OTA-S. Our analysis has led to the identification of specific morphological characteristics for each genotype, mainly depicting a larger ovule in the sexual genotype's reproductive development after the meiosis stage. These results reveal potentially important features, which could be used for a simple identification of genotypes. Furthermore, we have studied the localized expression of a gene found to be differentially expressed in contrasting genotypes of E. curvula. The gene SQUAMOSA PROMOTER BINDING PROTEIN-LIKE7 (SPL7) has been previously linked with flower development and abiotic stresses in several species, thus in situ hybridizations were carried out in the model plant Arabidopsis thaliana, as well as sexual and apomictic E. curvula genotypes. Differential expression was detected, specifically determining an overexpression of the gene in the sexual genotype. These results demonstrated that it could be an interesting candidate to understand the mechanisms behind apomictic development.